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As an one of the most promising materials of green energy as a photocatalyst for the production of hydrogen from renewable, natural sources (water, greenhouse gas) and environmental remediation through the degradation of toxic organic pollutants, graphite-like carbon nitride (characterized as a non-toxic and chemically highly resistant material) and its nanostructured and doped (especially by oxygen atoms) derivatives attract special attention. The actual task for expanding the scope of application of g-C 3 N 4 is to improve and optimize its catalytic, electronic and optical properties by increasing both the surface area of graphitic carbon nitride and the number of active centers of the carbon nitride network due to doping of carbon nitride. The use of a mixture of two different precursors ensures the creation of heterojunctions, and as a result, an improvement the photocatalytic characteristics of g-C 3 N 4 . The oxygen-doped carbon nitride (O-g-C 3 N 4 ) and water-soluble carbon nitride oxide (g-C 3 N 4 )O was simultaneously synthesized by the gas phase method under special reaction conditions of pyrolysis of cyanuric acid and urea mixture. Reduction by the hydroquinone of carbon nitride oxide (g-C 3 N 4 )O yields nanostructured reduced carbon nitride (or reduced multilayer azagraphene). Obtained products were characterized by using Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), chemical and X-ray diffraction (XRD) analyses, scanning electron microscopy (SEM). According to the results of XPS and IR spectrometry the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride (RCN) correspond to the bonds in a synthesized carbon nitride (SCN). However, according to XRD results, reduced carbon nitride (RCN) probably consists of poorly connected heteroatomic azagraphene layers, because it has a significantly larger (on 0.09 nm) interplanar distance between the adjacent nitrogen-carbon layers than interplanar distance between the layers of synthesized carbon nitride (SCN). By SEM characterization it was found that the pyrolysis of a mixture of various precursors (cyanuric acid and urea) yielded a product with smaller crystalline domains (which can improve photocatalytic characteristics) than the pyrolysis of a single precursor (urea only).

Sonochemical preactivation of moist gels of tin dioxide in the presence of additives of chromium(III) oxide, silver nitrate, and zinc acetate with subsequent heat thermal treatment leads to change in the porous and crystal structure of the resulted SnO2 samples obtained via doped with compounds of these metals. The doped samples have a narrower band gap and stronger absorption of visible light. Among the materials studied, Ag/SnO2 displays the highest photocatalytic activity in the oxidation of rhodamine B, safranin T, methyl orange, and phenol upon irradiation with visible light.

The chemical and structural modification of thin nanoporous graphitized carbon film was achieved by RF plasma treatment in the atmosphere of Ar, N2 and H2 + N2. The effect of carbon surface modification on the resistive sensitivity of gas sensor to water and ammonia vapors is studied. It was shown, that nitrogen and forming gas plasma treatments result in the same surface morphology (short and long-range behavior) and chemical modifications (introduction of pyridinic and pyrrolic nitrogen bonds), without noticeable changes of the film thickness and porosity. Such plasma treatments lead to surface hydrophilicity (on macro- and micro-levels) with increased surface energy and reduction of sensitivity to water vapor (from 22% to 3%), while adsorption rate and sensitivity to ammonia vapor increase. Argon treated film was found to have lower surface roughness, concentrations of oxygen and nitrogen bonds, which results in strong increasing of hydrophobicity and decreasing of water vapor sensitivity (to 8%).

We report on studies of the process of cyclic hydriding–dehydriding (eight cycles) of a mechanical alloy synthesized in a ball mill by grinding powder mixture Mg + 10 wt.% TiH2 + 10 wt.% Fe in argon medium. Hydrogen-sorption properties and thermal stability of the mechanical alloy are studied employing thermodesorption spectroscopy at hydrogen pressure of 0.1 MPa. Hydrogen capacity of the mechanical alloy is determined to be 4.9 wt.%, and onset temperature of hydrogen desorption from the alloy under this study equals 220°C. Kinetics of the process of hydrogen desorption from the hydride phases of the mechanical alloy is examined. The present studies have revealed that mechanical treatment of the magnesium powder in Ar medium with both Fe and Ti additives causes a greater effect on improving the kinetics of hydrogen desorption from hydride phase MgH2 of the alloy and decreasing its thermal stability in comparison with that caused by mechanical treatment of the same powder with either Fe or Ti additives in hydrogen medium.

The new method is suggested of formation of highly porous graphite-like thin films by radio frequency magnetron plasma enhanced chemical vapor deposition from argon-methane gas mixture. The prepared films were characterized before and after thermal annealing by XPS, XES, FTIR, Raman spectroscopy, XRD, XRR, AFM, and electrical measurements. Deconvolution of XPS spectra has demonstrated a significant growth of sp2/sp3 ratio from 1 for as-deposited films to 12 for the films annealed at 650 °C for 5 min. FTIR spectra have confirmed that thermal annealing results in reduction of H– and OH– functional groups and formation of С С bonds. The analysis of Raman spectra has shown that the annealing incorporates additional defects in graphite plane. XRD has shown that films are amorphous. Estimation of porosity from XRR measurements gave values of about 59% for as-deposited films and 34% for annealed films. AFM has shown that roughness of the films decreases from 3.3 to 0.6 nm during treatment at 650 °C in inert atmosphere. The size of pores was found to be few tens of nanometers. The electrical measurements have shown that after annealing the resistivity decreases by up to 5 orders of magnitude. Annealed films have demonstrated perceptible sensitivity to ammonia and water vapor.

First-principles band-structure augmented plane wave +local orbitals (APW+LO) calculations as incorporated in the WIEN2k code as well as X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) measurements are performed to elucidate the electronic structure of Zr4Fe2O oxide, a very prospective hydrogen-storage material. Total and partial densities of states for Zr4Fe2O are derived from the APW+LO calculations. The XPS valence-band spectrum as well as the XES Zr Lβ2,15, Fe Lα and O Kα bands are measured for Zr4Fe2O0.6 oxide. Our APW+LO calculations show that the O 2p-like states make the major contributions at the bottom of the valence band, whilst the Fe 3d- and Zr 4d-like states are the dominant contributors at the top of the valence band and at the bottom of the conduction band of Zr4Fe2O. Peculiarities of the occupation of the valence band of Zr4Fe2O predicted by the APW+LO calculations are confirmed experimentally by comparison, on the common energy scale, of the XPS valence-band spectrum and the XES bands representing the energy distributions of the Zr 4d-, Fe 3d- and O 2p-like states in the compound under consideration. In addition, the XPS Zr 3d, Fe 2p and O 1s core-level binding energies are derived for Zr4Fe2O0.6 oxide.

Electronic properties of Zr 3 V 3 O oxide, a very promising hydrogen-storage material, were studied both from theoretical and experimental points of view employing the full potential linearized augmented plane wave (FP-LAPW) method as well as X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). Total and partial densities of states of the constituting atoms of Zr 3 V 3 O have been derived from the FP-LAPW calculations. These data indicate that, the O 2p-like states are the dominant contributors in the bottom of the valence band, whilst the top of the valence band and the bottom of the conduction band of Zr 3 V 3 O are dominated by contributions of the V2 3d-like states, with slightly smaller contributions of the V1 3d-like states as well. Significant contributions of the Zr 4d-like states throughout the whole valence-band region and near the bottom of the conduction band are also characteristic of the electronic structure of Zr 3 V 3 O. The XPS valence-band spectra and the XES Zr Lβ 2,15 , V L α and O K α bands have been derived and compared on a common energy scale for Zr 3 V 3 O and Zr 3 V 3 O 0.6 oxides. This comparison of the experimental spectra was found to be in excellent agreement with the results of the FP-LAPW calculations. In addition, the XPS Zr 3d, V 2p and O 1s core-level binding energies have been measured for Zr 3 V 3 O and Zr 3 V 3 O 0.6 oxides.

X-ray photoelectron core-level and valence-band spectra for pristine and Ar + -ion irradiated (001) surfaces of KPb 2 Br 5 , K 0.5 Rb 0.5 Pb 2 Br 5 , and RbPb 2 Br 5 single crystals grown by the Bridgman method have been measured and fundamental absorption edges of the ternary bromides have been recorded in the polarized light at 300 K and 80 K. The present X-ray photoelectron spectroscopy (XPS) results reveal high chemical stability of (001) surfaces of K x Rb 1− x Pb 2 Br 5 ( x =0, 0.5, and 1.0) single crystals. Substitution of potassium for rubidium in K x Rb 1− x Pb 2 Br 5 does not cause any changes of binding energy values and shapes of the XPS constituent element core-level spectra. Measurements of the fundamental absorption edges indicate that band gap energy, E g , increases by about 0.14 and 0.19 eV when temperature decreases from 300 K to 80 K in KPb 2 Br 5 and RbPb 2 Br 5 , respectively. Furthermore, there is no dependence of the E g value for KPb 2 Br 5 upon the light polarization, whilst the band gap energy value for RbPb 2 Br 5 is bigger by 0.03–0.05 eV in the case of E ‖ c compared to those in the cases of E ‖ a and E ‖ b .

The TiLα, FeLα and OKα ultrasoft X-ray emission bands obtained in experiment reflect, respectively, the energy distribution of mainly the Ti3d, Fe3d and O2p electronic states in Ti4Fe2O compound, which is an efficient hydrogen absorber for energy cells. Full and partial densities of electronic states for all atoms constituting the indicated oxide were calculated by a modified method of associated plane waves (APW) using the WIEN2k software package. The APW calculation data for Ti4Fe2O compound as well as superposition of TiLα, FeLα and OKα ultrasoft X-ray emission bands on a single energy scale indicate that O2p states in the oxide are localized mainly near the bottom of the valence band, the major contribution near the ceiling of the valence band belonging to Fe3d and Ti3d states. According to the APW calculation, the major contribution to the bottom of Ti4Fe2O conduction band is made by Fe3d* and Ti3d* states. The APW data for Ti4Fe2O are supported by the cluster calculation performed for this compound using a FEFF82 software package.

— The electronic structure of hexagonal WO3 and triclinic CuWO4 nanocrystals, prospective materials for renewable energy production and functional devices, has been studied using the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) methods. The present XPS and XES results render that the W 5d-and O 2p-like states contribute throughout the whole valence-band region of the h-WO3 and CuWO4 nanocrystalline materialls, however maximum contributions of the O 2p-like states occur in the upper, whilst the W 5d-like states in the lower portions of the valence band, respectively.

Soft X-ray emission and absorption spectroscopy methods were used in the present work to study experimentally the electronic structure of the dense amorphous carbon phase synthesized in a mixture with diamond as a result of shock compression of carbon black. The X-ray emission C Kα bands, representing the energy distribution of the C 2p-like states, have been recorded for the amorphous carbon phase and, for comparison, for diamond, lonsdaleite, graphite, and carbon black. For the amorphous carbon phase, diamond and lonsdaleite the spectra of quantum yields of the X-ray photoeffect in the area of the C K absorption edge have been recorded as well. Total and partial densities of states of the carbon H-6 and bct-4 phases, diamond and lonsdaleite have been calculated using the first-principles self-consistent full potential linearized augmented plane wave (FP-LAPW) method. Comparison on a common energy scale of the X-ray emission C Kα bands and C K quantum yields of the dense amorphous carbon phase as well as the theoretical curves of partial C 2p-like states of the carbon H-6 and bct-4 phases reveals that, the electronic structure of the amorphous carbon phase under consideration is well described by that of the carbon bct-4 phase. The experimental X-ray emission and absorption spectroscopy data indicate that the amorphous carbon phase studied is metallic, being in agreement with the results of the theoretical FP-LAPW calculations.

Total and partial densities of states of constituent atoms of two tetragonal phases of Tl 3 PbCl 5 (space groups P4 1 2 1 2 and P4 1 ) have been calculated using the full potential linearized augmented plane wave (FP-LAPW) method and Korringa–Kohn–Rostoker method within coherent potential approximation (KKR-CPA). The results obtained reveal the similarity of occupations of the valence band and the conduction band in the both tetragonal phases of Tl 3 PbCl 5 . The FP-LAPW and KKR-CPA data indicate that the valence band of Tl 3 PbCl 5 is dominated by contributions of the Cl 3p-like states, which contribute mainly to the top and the central portion of the valence band with also significant contributions throughout the whole valence-band region. Further, the bottom of the valence band of Tl 3 PbCl 5 is composed mainly of the Tl 6s-like states, while the bottom of the conduction band is dominated by contributions of the empty Pb 6p-like states. The KKR-CPA results allow to assume that the width of the valence band increases somewhat while band gap, E g , decreases when changing the crystal structure from P4 1 2 1 2 to P4 1 . The X-ray photoelectron core-level and valence-band spectra for pristine and Ar + -ion-irradiated surfaces of a Tl 3 PbCl 5 monocrystal grown by the Bridgman–Stockbarger method have been measured.

Total and partial densities of states of the constituent atoms of ZrTiO4 and HfTiO4 titanates have been calculated using a self-consistent cluster method as incorporated in the FEFF8 code. The calculations reveal the similarity of the electronic structure of both titanates and indicate that the valence band of the compounds under consideration is dominated by contributions of O 2p states. These states contribute throughout the whole valence-band region; however their maximum contributions occur in the upper portion of the band. Other significant contributors in the valence-band region are Ti 3d and Zr 4d states in ZrTiO4 and Ti 3d and Hf 5d states in HfTiO4. All the above d-like states contribute throughout the whole valence-band region of the titanates; however maximum contributions of the Ti 3d states occur in the upper portion, whilst those of the Zr 4d (Hf 5d) states are in the central portions of the valence band. The FEFF8 calculations render that the bottom of the conduction band of ZrTiO4 and HfTiO4 is dominated by contributions of Ti 3d⁎ states, with also smaller contributions of Zr 4d⁎/Hf 5d⁎ and O 2p⁎ states. To verify the above FEFF8 data, the X-ray emission bands, representing the energy distributions of mainly O 2p, Ti 3d and Zr 4d states, were measured and compared on a common energy scale. These experimental data are found to be in agreement with the theoretical FEFF8 results for the electronic structure of ZrTiO4 and HfTiO4 titanates. Additionally, X-ray photoelectron valence-band and core-level spectra were recorded for the constituent atoms of the titanates under study.

Isobaric thermal desorption spectroscopy and X-ray diffraction analysis were used to study the influence of mechanical dispersion during high-energy milling γ-TiH 1.9 hydride upon its hydrogen-sorption characteristics, temperature and enthalpy of the γ → β (TiH 1.9 → Ti[H] β ) phase transition at isobaric heating the sample under hydrogen atmosphere with speed 3°/min. Isobars of hydrogen thermal desorption in the regions of the γ and β phases of the Ti–H 2 system at pressures of 0.1, 0.25, 0.315 and 0.45 MPa of hydrogen in the reactor have been derived. Experimental data obtained for initial titanium hydride and mechanically grinded for 20 min in a planetary ball mill have been used for construction of Van’t Hoff plots and for determination of enthalpy of formation of γ-hydride from solid solution of hydrogen in bcc titanium. Our experimental data reveal that 20 min high-energy influence on titanium hydride powder leads to increasing the specific surface of the samples from 0.13 to 8.58 m 2 /g and to significant (more than 250°) decreasing the temperature of the beginning of hydrogen release when heating the sample (i.e., to a decrease of thermal stability of mechanically activated TiH 1.9 ). However, mechanical dispersion does not change the temperature of the γ → β phase transition. It has been established that high-energy milling TiH 1.9 powder causes the effect of a decrease of enthalpy of the formation of γ-hydride from 248 kJ/mole H 2 to 175 kJ/mole H 2 .

Total and partial densities of states of the constituent atoms of iron tungstate, FeWO4, and cobalt tungstate, CoWO4, have been calculated using the first-principles self-consistent full potential linearized augmented plane wave (FP-LAPW) method. The results obtained reveal that the O 2p-like states are the dominant contributors into the valence band of the tungstates under consideration, whilst the bottom of the conduction band of FeWO4 and CoWO4 is dominated by contributions of the empty Fe 3d- and Co 3d-like states, respectively. The FP-LAPW data indicate that the O 2p-like states contribute mainly into the top of the valence band, with also significant contributions throughout the whole valence-band region, of FeWO4 and CoWO4 compounds. Other significant contributors into the valence-band region are the Fe 3d- and W 5d-like states in FeWO4 and the Co 3d- and W 5d-like states in CoWO4. All the above d-like states contribute throughout the whole valence-band region of the tungstates under consideration, however maximum contributions of the W 5d-like states occur in the lower, whilst the Fe (Co) 3d-like states in the upper portions of the valence band, respectively. To verify the above FP-LAPW data, the X-ray emission bands representing the energy distributions of mainly the valence O p-, Fe (Co) d-, Fe (Co) p- and W d-like states were measured and compared on a common energy scale with the X-ray photoelectron valence-band spectrum of the corresponding tungstate. The experimental data were found to be in good agreement with the theoretical FP-LAPW results for the electronic structure of FeWO4 and CoWO4 compounds.

Iron tungstate (FeWO 4 ) and cobalt tungstate (CoWO 4 ) nanostructures were prepared by the hydrothermal method using sodium tungstate (Na 2 WO 4 ·2H 2 O), ferrous ammonium sulfate [(NH 4 ) 2 Fe(SO 4 ) 2 ·6H 2 O] and cobalt chloride (CoCl 2 ·6H 2 O) solutions as precursors. The crystal structure and morphology of the as-prepared tungstates were characterized by X-ray diffraction analysis and transmission electron microscopy. The above characterizations render that the products obtained belong to the monoclinic crystal system and P2/a space group, with average sizes of nanoparticles of about 150 nm and 70 nm in the case of FeWO 4 and CoWO 4 , respectively. Electronic properties of the FeWO 4 and CoWO 4 tungstates were studied using several X-ray spectroscopy methods, mainly X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS). The XPS valence-band and core-level spectra, the XAS W L III edges (unoccupied W d-like states) as well as the XES bands reflecting the energy distribution of the valence W d- and O p-like states were recorded. The present XPS and XAS results reveal that the as-prepared FeWO 4 and CoWO 4 tungstates are in a composition close to a stoichiometric one. The XES results render that the W 5d- and O 2p-like states contribute throughout the whole valence-band region of the FeWO 4 and CoWO 4 tungstates, however maximum contributions of the O 2p-like states occur in the upper, whilst the W 5d-like states in the lower portions of the valence band, respectively.

Electronic properties of Ti 4 Fe 2 O oxide, a very promising hydrogen-storage material, were studied both from theoretical and experimental points of view employing the first-principles band-structure augmented plane wave + local orbitals (APW + LO) method with the WIEN2k code as well as X-ray photoelectron spectroscopy (XPS) and soft X-ray emission spectroscopy (SXES). Total and partial densities of states of the constituent atoms of Ti 4 Fe 2 O have been derived from the APW + LO calculations. The XPS valence-band spectra as well as the SXES Ti Lα, Fe Lα and O Kα bands have been measured for a series of Ti 4 Fe 2 O x oxides ( x = 1.0, 0.5, and 0.25). The present APW + LO calculations reveal that, the O 2p-like states are the dominant contributors into the bottom of the valence band, whilst the top of the valence band and the bottom of the conduction band of Ti 4 Fe 2 O are dominated by contributions of the Fe 3d- and Ti 3d-like states. The APW + LO results are confirmed experimentally by a comparison on a common energy scale of the XPS valence-band spectra and the SXES Ti Lα, Fe Lα and O Kα bands of the Ti 4 Fe 2 O x oxides. The XPS Ti 2p, Fe 2p and O 1s core-level binding energies have been measured for the compounds under consideration.

Total and partial densities of states of the constituent atoms of potassium yttrium double tungstate, KY(WO4)2 (KYW), have been calculated using the first-principles self-consistent full potential linearized augmented plane wave (FP-LAPW) method. The results derived reveal that the O 2p-like states are the dominant contributors into the valence band of KYW, while the conduction band of the compound is dominated by contributions of the W 5d-like states. The FP-LAPW calculations render that KYW is an indirect-gap material with the band-gap value of 3.645 eV. The X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) methods were also used in the present work to study experimentally electronic properties of potassium yttrium double tungstate. For the above compound, the XES bands reflecting the energy distribution of the valence W d-, O p- and K p-like states were derived and compared on a common energy scale with the X-ray photoelectron valence-band spectrum. Measurements of the energy shift of the XAS W LIII edge of KYW reveal that tungsten atoms are in the formal valence state 6+. A rather good agreement of the experimental XES and theoretical FP-LAPW data concerning electronic properties of KYW has been obtained in the present paper.

First-principles self-consistent band-structure calculations of copper tungstate, CuWO4, have been made using the full potential linearized augmented plane wave (FP-LAPW) method. Total and partial densities of states of the constituent atoms of CuWO4 have been derived. The results obtained reveal that the valence band of CuWO4 is dominated by contributions of the O 2p-like states, while the W 5d-like states are the main contributors into the conduction band of the tungstate. Additionally, the FP-LAPW calculations render that the W 5d- and Cu 3d-like states contribute mainly at the bottom and at the top of the valence band of CuWO4, respectively. In the present work, the X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) methods were also employed to investigate experimentally the electronic structure of copper tungstate. For the mentioned compound, the XES bands reflecting the energy distribution of mainly the W 5d-, Cu 3d- and O 2p-like states were derived and compared on a common energy scale with the X-ray photoelectron valence-band spectrum. A rather good agreement of the experimental and theoretical data concerning electronic properties of CuWO4 has been obtained in the present paper. Measurements of the energy shift of the XAS W LIII edge of CuWO4 clearly demonstrate that tungsten atoms in copper tungstate are in the formal valence state +6.

Electronic properties of cadmium selenogallate CdGa2Se4, a very promising electro-optical material, were studied both from theoretical and experimental points of view employing the ab initio band-structure augmented plane wave + local orbitals (APW + LO) method with the WIEN2k code and X-ray photoelectron spectroscopy (XPS). The present APW + LO calculations reveal that the Se p-like states are the dominant contributors into the top of the valence band of CdGa2Se4, while the bottom of the band is dominated by contributions of the Cd d-like states. Additionally, the bottom of the conduction band of the compound under consideration is dominated by contributions of the Ga s-like states. The present calculations render that the valence-band maximum and conduction band minimum in CdGa2Se4 are located at Γ resulting in a direct energy gap. The imaginary part of the electronic dielectric function ɛ(ω) was also calculated for the compound under consideration based on its band-structure data. The ɛxx(ω) and ɛzz(ω) components of the imaginary part of the electronic dielectric function reveal a considerable anisotropy in CdGa2Se4. The XPS valence-band spectrum of CdGa2Se4 has been derived and the binding energies of core-level electrons of the constituting atoms of the compound have been measured.

First-principles self-consistent band-structure calculations of potassium titanyl arsenate, KTiOAsO4 (KTA), have been made using the full potential linearized augmented plane wave (FP-LAPW) method. Total and partial densities of states of the constituent atoms of KTA have been derived. The results obtained show that the valence band of KTA is dominated by contributions of the O 2p-like states, while the Ti 3d-like states are the main contributors into the conduction band of the compound. Additionally, the FP-LAPW calculations have revealed that potassium atoms are highly ionized in KTA. In the present work, the X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) methods were also employed to investigate experimentally the electronic structure of potassium titanyl arsenate. For the mentioned compound, the XES K Ll ,T iL ,A sK2 and O K bands reflecting the valence K s-, Ti s,d-, As p- and O p-like states, respectively, were derived and compared on a common energy scale with the XPS valence-band spectrum. A rather good agreement of the experimental XES and XPS results and the theoretical FP-LAPW data for electronic properties of KTA has been obtained in the present paper. © 2008 Elsevier B.V. All rights reserved.

Intensive mechanical milling was used to synthesize a MgH 2 (50 wt.%) + TiB 2 (50 wt.%) composite. Thermal stability of the composite versus H-desorption was studied employing the thermodesorption spectroscopy (TDS) method. The TDS data have revealed that TiB 2 addition decreases the dissociation temperature of the MgH 2 hydride by about 50 °C. An X-ray photoelectron spectroscopy analysis has shown that TiB 2 addition does not alter the surface chemical state of particles of the MgH 2 hydride, a component of the composite under consideration. The effect of decreasing decomposition temperature of MgH 2 due to addition of TiB 2 has been attributed to catalytic influence of a TiB 2 particle surface on processes of associative hydrogen desorption taking place on the surface of MgH 2 particles, as well as to a higher degree of dispersion of magnesium dihydride provided by the presence of TiB 2 .

Influence of addition of some transition metals (TMs), mainly Ti, Mn, Fe and Ni, to magnesium upon thermal stability of the hydride phase MgH2 synthesized due to reactive mechanical alloying (RMA) in hydrogen atmosphere at pressure 1.2 MPa was studied employing the thermodesorption spectroscopy (TDS) method. The TDS spectra registered differ from each other by their shapes and fine-structure peculiarities. This fact allows to conclude about a different influence of the TMs under consideration upon the feature of hydrogen distribution on location sites in the hydride phase and, consequently, upon its decomposition temperature. We have made an attempt to elucidate the origin of the mentioned influence of the TMs upon the effects derived. A correlation between the degree of dispersion of TM alloying the MgH2 hydride and its decomposition temperature was observed. It has been established that, addition of 10 wt% Ti reveals the maximum influence on decreasing decomposition temperature of the hydride phase. The X-ray photoelectron O 1s core-level spectrum of the specimen contained the addition of 10 wt% Ti shows decreasing a quantity of oxygen-contained structures, catalyst poisons, adsorbed on its surface. © 2007 Elsevier B.V. All rights reserved.

X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) methods were employed in the present work to investigate the electronic structure of almost stoichiometric cubic (NaCl structure) HfxTa 1–xCy carbides. The XPS valenceband and core-level spectra, the XES bands reflecting energy distributions of mainly the Ta 5d- and C 2p-like states as well as the XAS Ta LIII edges (unoccupied Ta d-like states) were derived and compared on a common energy scale for cubic HfC0.95 ,H f 0.5Ta 0.5C0.94 and TaC0.98 compounds. To investigate the influence of substitution of tantalum atoms for hafnium atoms in the HfxTa 1–xCy carbides, cluster self-consistent calculations of total and partial densities of states were carried out with the FEFF8 code for HfC, Hf0.5Ta 0.5C and TaC compounds possessing the NaCl-type structure. In the present work a rather good agreement of the experimental and theoretical results for the electronic structure of the HfxTa 1−xCy system under study was obtained. The results indicate that a strong hybridization of the Hf(Ta) 5d- and C 2p-like states is characteristic for the HfxTa 1−xCy carbides. It has been established that, substitution of hafnium atoms by tantalum atoms in the HfxTa 1−xCy system reveals increasing the half-width of the XES C K band. When going from HfC0.95 to TaC0.98 through the carbide of intermediate composition, the main maximum of the XPS valence-band spectrum shifts in the direction opposite to the position of the Fermi level. In the above sequence of compounds the asymmetry index of the C K bands decreases significantly. © 2007 Elsevier B.V. All rights reserved.

Using poly(vinylidene fluoride) (PVDF) carbonization at 750° C in fine-particle silica and its mixtures with graphite, we have prepared carbon-loaded porous composites which offer benzene absorption from 0.90 to 1.52 ml/g, compressive strength of 6 MPa, and Brinell hardness of up to 18 MPa. We observed the formation of various nanostructures (spheres, spherical segments, and layered platelets) and sizes (several to hundred nanometers). X-ray photoelectron and energy dispersive x-ray spectroscopy data indicate the presence of C-C, C =C, CO, COO, and CHF groups on the carbon surface. X-ray emission spectroscopy data show that the silica matrix composite prepared via PVDF carbonization contains small carbon clusters weakly bonded to the matrix. The silica/graphite matrix composite contains multilayer carbon films strongly bonded to the matrix. The OK α spectra of both composites are similar to the spectrum of pure SiO2.

X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) methods were employed in the present paper to investigate the electronic structure of face-centred cubic (fcc) molybdenum dioxide, fcc-MoO2. For the mentioned compound, the XES O K and Mo L2,15 bands reflecting the valence O p- and Mo s,d-like states, respectively, were derived and compared on a common energy scale with the XPS valence-band spectrum. For comparison, the similar experimental studies of the electronic structure were made for a usual orthorhombic form of molybdenum trioxide, MoO3. Band-structure calculations of fcc-MoO2 were made using the full potential linearized augmented plane wave (FP-LAPW) method. A rather good agreement of the experimental XES and XPS results and the theoretical FP-LAPW data for the electronic properties of fcc-MoO2 has been achieved in the present paper. A new near-Fermi sub-band was detected on both the XES Mo L2,15 band and the XPS valence-band spectrum when going from orthorhombic MoO3 to fcc-MoO2. The FP-LAPW calculation reveals that the main contributors into the aforementioned sub-band of fcc-MoO2 are the Mo 4d(eg) states. Further, the FP-LAPW data indicate that the O 2p and Mo 4d(t2g) states contribute into both the central part and the bottom of the valence band of fcc-MoO2, while the Mo 4d(eg) states contribute almost exclusively into the bottom of the valence band of the oxide. A significant portion of density of states (mainly Mo 4d(eg) states) detected by the FP-LAPW calculation at the Fermi energy of fcc-MoO2 indicates that the oxide is rather unstable. © 2007 Elsevier B.V. All rights reserved.

Crystallographic and electronic parameters of KTiOAsO 4 (KTA) (001) surface have been studied with reflection high energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS). From analysis of RHEED patterns the superstructure formation has been detected with the relations a = a 0 , b = 2b 0 and c = 2c 0 were a 0 , b 0 and c 0 are the cell parameters of KTA bulk. Results of the core-level spectroscopy are discussed in comparison with those obtained earlier for other crystals belonging to the KTP family. The relationship between crystal structure variations and chemical shifts of binding energy of constituent element core-levels induced by element substitution or doping has been considered for a set of KTP family crystals including KTiOPO 4 , KTiOAsO 4 , TITiOPO 4 and K 0.77 Ti 0.77 Sb 0.23 OPO 4 .

The effect of 1.5 keV Ar+ ion irradiation on the (001) surfaces of potassium titanyl arsenate, KTiOAsO4 (KTA), has been investigated using reflection high-energy electron diffraction (RHEED) and X-...

X-ray photoelectron (XPS), emission (XES) and absorption (XAS) spectroscopy methods were used to study the electronic structure of cubic TaCxNy carbonitrides, where x+y≈1, and of rhombohedral Ta4C3 and TaC0.59N0.15 compounds. The XES Ta Lβ5, C Kα and N Kα bands and XAS Ta LIII edges for the cubic TaCxN∼1−x carbonitrides were studied and compared on a common energy scale, but the XPS valence-band spectra were studied for the rhombohedral compounds. The XPS core-level binding energies were measured for all the cubic and rhombohedral carbonitrides studied. Comparison on a common energy scale of the XES bands of the cubic TaCxN∼1−x compounds reveals that the strong hybridization of the Ta 5d- and C(N) 2p-like states is characteristic of the above carbonitrides, but the hybridization between the C 2p- and N 2p-like states is absent. Substitution of carbon atoms for nitrogen atoms in the studied cubic and rhombohedral tantalum carbonitrides leads to increasing the metallic and ionic components and decreasing the covalent component of the chemical bonding.

X-Ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) methods were used to study the electronic structure of rhombohedral Ta 4 C 3 and TaC 0.59 N 0.15 compounds, as well as of several samples of the cubic TaC x N ∼0.8− x system. The XPS valence band spectra and the XES Ta Lβ 5 bands were derived for the rhombohedral compounds, but the Ta Lβ 5 , N Kα and C Kα emission bands for the cubic TaC x N ∼0.8− x carbonitrides were studied and compared on a common energy scale. A strong hybridization of the Ta 5 d -like and C(N) 2 p -like states is characteristic of the compounds of the TaC x N ∼0.8− x system studied, but the hybridization between the C 2 p -like and N 2 p -like states is absent. The substitution of carbon atoms for nitrogen atoms leads to increasing the metallic and ionic components and decreasing the covalent component of the chemical bonding in both systems studied. However, the metallic component is somewhat higher, but the ionic component is smaller to some degree in the rhombohedral compounds compared with those of cubic TaC x N ∼0.8− x system for specimens possessing similar nitrogen-to-carbon ratios.

We have used neutron diffraction and magnetic measurements to investigate the changes in magnetic properties of the Kondo semimetal compound CeNiSn after charging with deuterium gas under moderate conditions. Charging with deuterium led to the formation of the monodeuteride CeNiSnD with filled TiNiSi structure. This compound gives rise to long-range antiferromagnetic ordering below T N =5.1 K. The ordered magnetic moment value equals 1.37(3) μ B per Ce atom, the moments pointing along the [001] direction. No significant ordered magnetic moment on the Ni atoms has been observed by powder neutron diffraction.

This work focused on studies of the phase composition and crystal structure of La x Mm 1-x Ni 4.7 Sn 0.3 (x=0, 0.5 and 1.0) alloys, where Mm denotes La-rich mischmetal produced by Norsk Hydro ASA. The alloys have been studied using conventional powder and synchrotron X-ray diffraction (XRD), powder neutron diffraction and scanning electron microscopy (SEM). After annealing at 950°C the alloys were nearly single-phase materials with small precipitations of RENiSn equiatomic intermetallics formed at grain boundaries. Hydrogen absorption-desorption studies at 298, 323 and 348K showed (a) a 'flat' structure of the pressure-composition isotherms; (b) a rather broad range of working H storage capacities; (c) an increase of the plateau pressures and decrease in both enthalpy and entropy changes following an increase of the Mm content in the alloy; and (d) fast formation-decomposition rate. Desorption isotherms were approximated by a recently developed model of phase equilibria in the metal-hydrogen systems. In situ powder neutron diffraction studies of the system MmNi 4.7 Sn 0.3 -D 2 show that in the region of α-solid solution deuterium insertion leads to a gradual increase of the unit cell volume reaching 1.9%. In the hexagonal β-MmNi 4.7 Sn 0.3 D 4.51 deuteride D atoms occupy two of four available types of tetrahedral interstices including 6m RE 2 (Ni,Sn) 2 and 12n RE(Ni,Sn) 3 .

X-Ray photoelectron (XPS), emission (XES) and absorption (XAS) spectroscopy methods were used to study the electronic structure of hexagonal tungsten trioxide, h-WO3. Its precursor, hexagonal hydrogen tungsten bronze, HxWO3, and the monoclinic form of tungsten trioxide, m-WO3, were also studied. For the mentioned compounds, both the XPS valence-band and core-level spectra, as well as the O Kα emission bands and the W LIII absorption edges were derived. It was established that, binding energies of both the W 4f and O 1s core-level electrons do not change when going from the tungsten trioxides to HxWO3. A high-energy shift of the inflection point of the XAS W LIII spectrum of the HxWO3 bronze, with respect to its position on the spectrum of pure metallic tungsten, was found to be close to those of the spectra of the two WO3 forms studied. Half-widths of both the XPS valence-band spectra and the O Kα bands increase somewhat in the sequence m-WO3→h-WO3→HxWO3. The formation of a near-Fermi sub-band, which is absent for both the modifications of WO3, was observed on the XPS valence-band spectrum of hexagonal HxWO3. The energy positions of the centers of gravity of the O Kα band remain constant for all the compounds studied.

X-ray photoelectron (XPS), emission (XES), and absorption (XAS) spectroscopy methods were used to study the electronic structure of WO compounds over the range 2.0# x # 3.0. The XPS core-level binding energies (BEs) and valence-band structures for the tungsten x oxides were determined. The XES O Ka and XAS W L spectra for the compounds were derived. It was established that the XPS O III 2s-like sub-band intensity decreases almost monotonously when going from WO to WO . In all the studied tungsten oxides the energy 32 positions of the centers of gravity of the O 2p-like emission bands remain constant. Half-widths of both the XPS W 4f and O 1s core-level spectra increase in the sequence WO φιWO . The creation of a sub-band of M‐M interactions with a two-peak structure in the 32 near-Fermi region of the XPS valence-band spectra was observed for WO , where 2.0# x # 2.77. The sub-band intensity increased x significantly in the sequence WO φιWO φιWO . The XPS O 1s core-level BEs remain constant (within experimental error) for all 2.77 2.3 2 the tungsten oxides studied. Both the O Ka band and the XPS valence-band spectra broaden somewhat in the sequence WO φιWO . The 32 inflection point of the W L absorption spectra shifted almost monotonously towards higher energies when going from WO to WO .

The CdGa2Se4 compound, with a crystalline lattice of defect chalcopyrite, shows birefringence. However, in contrast to the similar CdGa2S4 compound, CdGa2Se4 has no experimentally observed isotropic points in the optical spectral range. In this study, the electron energy structure and optical spectra of CdGa2Se4 are calculated for three different experimentally obtained sets of crystalline parameters. Only one of these sets shows the absence of isotropic points.

The electronic structure and charge states of atoms of cubic and hexagonal tantalum carbides have been studied by X-ray photoelectron (XPS) and X-ray absorption (XAS) spectroscopy. The XPS spectra of both valence and core-level electrons as well as the TaLIII XAS spectra of TaCx have been obtained over the range 0.36≤x≤0.98. In all the tantalum carbides studied charge transfer takes place from Ta to C atoms. The shifts of the Ta 4f core levels and the midpoints of the TaLIII absorption edges indicates that the effective positive charge of the Ta atoms decreases in the row TaC0.98»TaC0.36. In that sequence of compounds the main peak of the XPS valence band spectra shifts toward the Fermi level by about 0.85 eV.

The photoelectron spectrograms of the Ni2p, Ni3p, Co3p, Mn2p, Al2p,Ols and Cls in LaNi4.6Mn0.4, LaNi4.5Al0.5, MmNi3.5Co0.7Al0.8, and Zr3d, Ti2p, V2p, Ni2p, Co2p, Ols, and Cls inZr0.9VCo0.55Ni0.55 and Zr0.59Ti0.41V0.53Cr0.22 Fe0.20Co0.27Ni0.78 have been obtained.In a surface layer about 2–2.5 nm of both alloys, the main part of nickel atoms are in metallic state(Ni0) and only a third of them in oxidized state (Ni+2, Ni+3). At the same time the concentration of nickel in surface layer of Zr-containing alloy is muchlower as compared with Mm-containing alloy. The chemical state of Co and V atoms is similar toNi atoms state, but their concentrations, especially of V, in surface layer is lower than that ofnickel. The results of XPS have been compared with those of transmission electron microscopy ofthe thin foils of La- and Zr- based alloys. Dark field microphotographs of the oxidized alloysindicate presence of two different phases, which, according to electron microdiffraction, arenickel-based alloy and oxide. On the first stage of oxidation on the surface of foil the fine nickelparticles (about 10 nm) and amorphous oxide phase appear. Complete oxidation of the foil leadsto formation of eutectic-like structure of mixture of metallic and oxide phase. Some difference ofthe oxidized layer structure of investigated alloys have been observed.

The X-ray emission spectroscopy (XES) method has been used to study the electronic structure of substoichiometric tantalum mononitrides. Both the Ta Lβ 5 and N Kα X-ray emission spectra of cubic nitrides TaN x (Nacl structure, 0.81 ≤ x ≤ 1.172), hexagonal nitrides TaN 0.99 (CoSn structure) and TaN 0.90 (WC structure) have been derived and compared on a common energy scale. In the sequence TaN (CoSn structure) → TaN (WC structure) → TaN (NaCl structure) a decrease of the N Kα band halfwidth was observed. In most substoichiometric cubic tantalum mononitrides with vacancies on the metal sublattice (1.134 ≤ x ≤ 1.172) a subband of non-bonding N 2p-like states appeared in the energy region between the Ta 5d-N 2p- and Ta Sd-like bands. In all tantalum nitrides studied the Ta 5d-like and N 2p-like states are strongly hybridized, and a charge transfer occurs from Ta to N atoms.

X-ray photoelectron (XPS), emission (XES), and absorption (XAS) spectroscopy methods have been used to study the electronic structure of cubic Tacx and hexagonal Ta2Cy (y=2x) carbides. The XPS core-level binding energies (BE's) and valence-band structures for TaCx over the range 0.36x0.98 have been determined. The XES bands and XAS edges in all studied compounds have been derived and compared in a single energy scale with the XPS valence-band spectra. In all tantalum carbides the Ta 5d-like and C 2p-like states are strongly hybridized, and the charge transfers from Ta atoms to C atoms. It was established that E1 was generally lowered by the introduction of C-vacancies in cubic tantalum carbides, and additional vacancy states appeared in the XPS valence-band spectra of these substoichiometric compounds. In the row TaC0.98→TaC0.75→TaC0.50→TaC0.36 the XPS Ta 4f and C 2s core-level BE's and main peaks of the XPS valence-band spectra shifted toward the Fermi level by 0.5 to 0.85 eV, while the C Is BE's remained constant (within the experimental error) for all studied substoichiometric tantalum carbides. In this row some shifts (0.6 to 0.9eV) of the main maxima of the XES Ta 5d-like and C 2p-like bands toward E1 are observed. In the mentioned row the intensity of the XPS valence-band spectra normalized on the peak intensity of the XPS Ta 4f7/2, 5/2 core-level spectra, decrease almost monotonously. The C Kα band half-width decreases by about 0.3 eV going from cubic TaCx carbides to hexagonal Ta2Cy carbides, but the C Kα band asymmetry index increases from 0.72 in TaC0.98 to about 1.75 in the carbides Ta2Cy. In all studied substoichiometric tantalum carbides the energy positions of the centres of gravity of the C 2p-like emission bands remain constant.

X-ray photoelectron (XPS), emission (XES), and absorption (XAS) spectroscopy methods have been used to study the electronic structure of cubic TaCx and hexagonal Ta2Cy (y=2x) carbides, and also rhombohedral ζ-Ta4C3 and ϵ-Ta3C2 phases. The XPS core-level binding energies (BEs) and valence-band structures for TaCx over the range 0.36≤x≤0.98 have been determined. It was established that Ef was generally lowered by the introduction of C-vacancies in cubic tantalum carbides. The results of the XPS and XES studies indicate that the layered subcarbides ζ-Ta4C3 and ϵ-Ta3C2 are individual phases and are by no means a simple mixture of the cubic TaCx and hexagonal Ta2Cy carbides. In the layered subcarbides ζ-Ta4C3 and ϵ-Ta3C2 the formation of new (shortened) M–M bonds between the tantalum atoms neighbouring the {111} plane of the carbon sublattice, where the C-vacancies concentrate, results in the appearance of an additional peak (EBE≈2 eV below Ef) in the XPS valence-band spectra. In the row TaCx→ζ-Ta4C3→ϵ-Ta3C2→Ta2Cy the XPS Ta 4f and C 2s core-level BEs and main peaks of the XPS valence-band spectra shifted toward the Fermi level by about 0.5 eV, while the C 1s BEs remained constant (within the experimental error) for all studied subcarbides. In this row some shifts of the main maxima of the XES Ta 5d-like and C 2p-like bands toward Ef are observed. In all tantalum carbides the charge transfers from Ta atoms to C atoms.

X-ray emission spectroscopy (XES), X-ray absorption spectroscopy (XAS), and X-ray photoelectron spectroscopy (XPS) methods were used to study the electronic structure of WGe 2 , W 5 Ge 3 , and MoGe 2 compounds formed in a high temperature-high pressure treatment. Transformations of the electronic structure after termination of the α → β irreversible polymorphic transitions in the tungsten and molybdenum digermanides have been investigated. The XES bands and XAS edges in all compounds studied have been derived and compared in a single energy scale. The XPS core-level binding energies have been determined. In the germanides a small amount of charge transfers from the Ge atoms to the M atoms (M - W, Mo). In the molybdenum and tungsten germanides the M d(p)-like valence states and Ge 4p-like states are strongly hybridized.

The surface conditions of powder compounds Ti4Fe2Ox (x = 0.5; 1.0) have been studied by means of the XPS method. As in the case of the alloys, Ti1.1 Fe, Ti1.1Fe0.9Mn0.1 and Ti1.1Fe0.8Cu0.1Ni0.1 studied earlier the peculiarities of the XPS O 1s core-level spectra in Ti4Fe2Ox are also observed. The peculiarities can be connected with oxygen-containing gas molecules chemisorbed on the alloy surfaces. The dependence of activation temperature upon the type of oxygen-containing structures absorbed on the alloy surfaces has been established. A physical model of the activation process for TiFe-based alloys is proposed. In this model, the surface oxides play an active role in distinction from the segregation model where the oxides play a passive role.

X-ray emission spectroscopy (XES), X-ray absorption spectroscopy (XAS), and X-ray photoelectron spectroscopy (XPS) methods were used to study the electronic structure of WGe 2 , W 5 Ge 3 , and MoGe 2 compounds formed in a high temperature-high pressure treatment. Transformations of the electronic structure after termination of the α → β irreversible polymorphic transitions in the tungsten and molybdenum digermanides have been investigated. The XES bands and XAS edges in all compounds studied have been derived and compared in a single energy scale. The XPS core-level binding energies have been determined. In the germanides a small amount of charge transfers from the Ge atoms to the M atoms (M - W, Mo). In the molybdenum and tungsten germanides the M d(p)-like valence states and Ge 4p-like states are strongly hybridized.

Electronic properties of cadmium selenogallate CdGa2Se4, a very promising electro-optical material, were studied both from theoretical and experimental points of view employing the ab initio band-structure augmented plane wave + local orbitals (APW + LO) method with the WIEN2k code and X-ray photoelectron spectroscopy (XPS). The present APW + LO calculations reveal that the Se p-like states are the dominant contributors into the top of the valence band of CdGa2Se4, while the bottom of the band is dominated by contributions of the Cd d-like states. Additionally, the bottom of the conduction band of the compound under consideration is dominated by contributions of the Ga s-like states. The present calculations render that the valence-band maximum and conduction band minimum in CdGa2Se4 are located at Γ resulting in a direct energy gap. The imaginary part of the electronic dielectric function ɛ(ω) was also calculated for the compound under consideration based on its band-structure data. The ɛxx(ω) and ɛzz(ω) components of the imaginary part of the electronic dielectric function reveal a considerable anisotropy in CdGa2Se4. The XPS valence-band spectrum of CdGa2Se4 has been derived and the binding energies of core-level electrons of the constituting atoms of the compound have been measured.

Thermal stability and hydrogen sorption properties of the MgH2 phase derived by the reactive milling of the Mg + 10 wt% Ti mixture was studied by the thermodesorption spectroscopy method during the first five cycles of hydrogen sorption-desorption. The addition of Ti decreases decomposition temperature of MgH2by 115 K, if we conclude about decomposition temperature taking into account peaks of speed of a hydrogen release on the desorption spectra derived during the first cycle of heating-cooling in hydrogen atmosphere of the Mg + 10 wt% Ti mechanical alloy. During the second cycle of dehydriding-hydriding, the decomposition temperature of the MgH2 phase of the Mg + 10 wt% Ti composite decreases additionally by 35 K, and the temperature does not change for three following sorption-desorption cycles. It has been established the influence of the method of synthesis of the hydride phase MgH2upon location sites of hydrogen in the phase, and, consequently, upon its decomposition temperature. The addition of titanium to magnesium increases the effect of the above influence and promotes increasing the process of dispersion of magnesium and the MgH2 hydride synthesized due to the reactive milling. Additionally, the addition of titanium promotes decreasing the quantity of oxygen-containing structures, catalytic poisons preventing dissociative hydrogen chemosorption, adsorbed on the surface of MgH2 particles.

The electronic structure of face-centred cubic (fcc) MoO x (x = 1.9) oxide derived due to reduction of hydrogen bronze H1.63MoO3 has been studied using the X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) methods. For comparison, the electronic structure of molybdenum trioxide, MoO3, and the H1.63MoO3 bronze was studied as well. The XES O Kα and Mo Lβ2,15 bands of fcc-MoO1.9 and XPS valence-band spectra of the MoO1.9, MoO3 and H1.63MoO3 compounds were derived. Band structure calculations of fcc-MoO2 have been fulfilled using the full-potential linearized augmented plane wave (FP-LAPW) method. The theoretical XES O Kα and Mo Lβ2,15 bands were calculated for fcc-MoO2 employing the above method. A rather good agreement of shapes of experimental and theoretical XES O Kα and Mo Lβ2,15 bands for fcc molybdenum dioxide has been obtained.

X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES) and near-edge X-ray absorption fine structure (NEXAFS) methods were applied to study the electronic structure of copper tungstate, CuWO 4 . For the compound, XP valence-band spectra with different energies of excitation were studied, as well as the XE O Kα band and the NEXAFS O 1s spectrum were derived. The binding energies of the XP core-level electrons of the constituting elements of CuWO 4 were measured. For comparison, some spectra of the hexagonal form of tungsten trioxide, h-WO 3 , were investigated. It was found that the half-width of the O Kα band decreases somewhat but that of the XP valence-band spectrum increases when going from h-WO 3 to CuWO 4 , however the energy positions of the maxima and of the centres of gravity of the O Kα band remain constant for the above compounds. Measurements of the XP O 1s core-level binding energies and of the energy positions of the inflection point of the NEXAFS O 1s spectra reveal that the effective negative charge of oxygen atoms in CuWO 4 is close to that in h-WO 3 , while XPS W 4f core-level measurements reveal that the positive effective charge of tungsten atoms decreases somewhat in the sequence h-WO 3 → CuWO 4 .

The X-ray photoelectron La 3d, Ni 2p, Ni 3p, Al 2p, O Is and C 1s core-level spectra in LaNi4.5Al0.5 and the Zr 3d, Ti 2p, Ni 2p, Co 2p, V 2p, O 1s and C 1s spectra in Zr0.59Ti0.41Ni0.78V0.53Cr0.22Fe0.2Co0.27 and Zr0.9VCo0.55Ni0.55 have been obtained. Results of the XPS studies have been compared with data of polarization measurements as well as of the electrochemical behaviours of the alloys in the potential range -0.95 V ≤ E ≤ -0.2 V. A good correlation of data of the XPS and polarization measurements is established. The present study indicate that the alloy which contained on its surface the greatest amount of catalytic active centres observed by the XPS technique (e.q., segregation of the nickel atoms in the metalic state Ni°) possesses the more flat polarization curve in the range of small currents as well as the smaller potential at some cathodic currents. In the present work the such alloy was LaNi4.5Al0.5, which displayed higher electrochemical activity as compared with those of the Zr-containing alloys.